Buck converters are commonly used in electronics for changing the voltage or polarity of a power supply. Buck converters typically employ two electronic switches (typically MOSFETs) in combination with an output inductor. The switches are alternately turned on, thereby providing voltage pulses to the output inductor.
During portions (dead times) of the switching cycle, both switches are off. When both switches are off, the output inductor produces freewheeling current that flows through the integral body diode of one of the switches. Body diode current produces substantial energy loss due to the forward-bias voltage drop across the diode, thereby reducing the energy efficiency of the buck converter. In order to improve the efficiency of buck converters, the dead time must be reduced as much as possible.
Another source of loss in buck converters is driver loss. In conventional buck converters, energy required to charge the switch gates is dissipated in the driver circuit. This energy loss substantially affects the converter efficiency.
In order to provide buck converters with small size and weight, and reduced cost, it is best to operate the buck converter at high frequency. However, energy loss from both body diode conduction and driver loss increase with increasing operating frequency. Body diode conduction and driver loss tends to limit the maximum operating frequency of buck converters.